Does Your Metabolism Slow Down With Age? What the Research Shows

"My metabolism isn't what it used to be" is something I hear a lot. The good news is that newer research tells a more hopeful story than the old idea of a steady slowdown from your 20s. Here's what actually changes, and what you can do about it.

What is metabolism?

Your metabolism is all the chemical processes that keep you alive, from breathing and circulating blood to turning food into energy. The biggest part is your basal metabolic rate (BMR): the energy your body uses at rest just to keep running. It makes up about 50–70% of the energy you use each day. The rest comes from physical activity and from digesting food.

Muscle uses more energy than fat, even at rest. So the more muscle you carry, the more energy your body tends to use.

Does your metabolism slow down with age?

Less than you might expect. A large 2021 study measured daily energy use in people aged from 8 days to 95 years. Once body size and composition were taken into account, energy use:¹

• peaked at around age 1, at about 50% above adult levels;
• slowly fell to adult levels by about age 20;
• stayed stable from 20 to 60, even during pregnancy;
• declined gradually after 60.

So the idea that your metabolism drops sharply in your 30s or 40s isn't supported. Much of the change people notice in mid-life comes from other things you can influence.

Why do people gain weight in mid-life?

As we get older, most of us gradually lose muscle and gain fat, especially if we become less active. Less muscle means your body uses a little less energy each day. Busy lives, less incidental movement, poorer sleep and changing eating habits can all add up. The good news is that each of these can be changed.

How can you support your metabolism as you age?

Do strength training and eat enough protein

Building and keeping muscle is the most useful thing you can do. Australian guidelines recommend muscle-strengthening activity on at least 2 days a week.⁶ Eating more protein alongside strength training leads to greater gains in muscle and strength, with little extra benefit above about 1.6 g of protein per kg of body weight a day.² Protein is also the most filling nutrient, which can help with appetite.

Keep moving, and add some intervals

Australian guidelines recommend at least 30 minutes of moderate to vigorous activity on most days.⁶ High-intensity interval training (HIIT) does raise your energy use for a while after exercise, often called the "after-burn". But the effect is small: roughly 100–300 kJ extra after a session.³ Choose the kind of exercise you enjoy and will keep doing.

Get enough sleep

Short sleep doesn't slow your metabolism, but it does change how much you eat. A meta-analysis found that people who had their sleep cut short ate about 1,600 kJ more the next day, with no change in the energy they used.⁴ Aim for 7–9 hours with consistent bed and wake times.⁶

Avoid very strict diets

Very low-energy diets make it hard to get enough nutrients and protein, and can cost you muscle. You may have heard of "starvation mode". Your body can use slightly less energy after weight loss, but in well-designed studies the effect is small and tends to fade once your weight settles.⁵ A steady, sustainable approach works better than a crash diet.

Can a thyroid problem slow your metabolism?

Yes. Your thyroid gland plays a major role in regulating metabolism, and an underactive thyroid can slow it down. Tiredness, feeling cold and unexplained weight gain can have many causes, but if you're concerned, your practitioner can advise whether thyroid testing is worthwhile.

Quick tips for a healthy metabolism

• Do strength training on at least 2 days a week.
• Include protein at each meal.
• Move more through the day and break up long periods of sitting.
• Prioritise sleep: 7–9 hours a night.
• Skip fad diets that cut out whole food groups or are very low in energy.
• Cut back on alcohol.

Frequently asked questions

Does metabolism slow down with age?

Not much until later life. Once body size is taken into account, metabolism is fairly stable from about 20 to 60 and then declines gradually.

At what age does your metabolism slow down?

Research suggests the gradual decline starts after about 60. Changes before then are mostly linked with losing muscle and moving less.

How can I boost my metabolism as I get older?

Strength training on at least 2 days a week, eating enough protein and staying active help you keep muscle, which uses more energy than fat.

Does HIIT boost your metabolism?

HIIT raises energy use for a while after exercise, but the extra is small. Choose exercise you enjoy and can do regularly.

Does dieting slow your metabolism?

Your body may use slightly less energy after weight loss, but the effect is usually small and fades once your weight stabilises.

References

Research (PubMed)

1. Pontzer H, Yamada Y, Sagayama H, et al. Daily energy expenditure through the human life course. Science. 2021;373(6556):808–812. PubMed 34385400
2. Morton RW, Murphy KT, McKellar SR, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med. 2018;52(6):376–384. PubMed 28698222
3. Panissa VLG, Fukuda DH, Staibano V, Marques M, Franchini E. Magnitude and duration of excess of post-exercise oxygen consumption between high-intensity interval and moderate-intensity continuous exercise: a systematic review. Obes Rev. 2021;22(1):e13099. PubMed 32656951
4. Al Khatib HK, Harding SV, Darzi J, Pot GK. The effects of partial sleep deprivation on energy balance: a systematic review and meta-analysis. Eur J Clin Nutr. 2017;71(5):614–624. PubMed 27804960
5. Nunes CL, Casanova N, Francisco R, et al. Does adaptive thermogenesis occur after weight loss in adults? A systematic review. Br J Nutr. 2022;127(3):451–469. PubMed 33762040

Australian guidelines

6. Australian Government Department of Health, Disability and Ageing. 24-hour movement guidelines: recommendations for adults (18 to 64 years). View source

This article is general information and isn't a substitute for personalised advice. Speak to your practitioner about your situation.